Mortality and morbidity from cardiovascular toxicities of recreation use of cocaine has increased alarmingly in the United States. However, the prevalence of cardiovascular abnormalities in cocaine addicts is unknown, nor do we know the mechanism by which cocaine, both acute and long-term uses, adversely affects cardiac function and coronary circulation. Thus we propose the study with the following objectives: a) to determine the effects of long-term use of cocaine on cardiac function in 100 male cocaine addicts and b) to determine the effects of acute cocaine administration (48 mg I.V.) on the cardiovascular system in male cocaine addicts with possible emphasis on possible pathophysiologic mechanisms of cocaine-related acute myocardial infarction and sudden deaths. The proposed study embraces four protocols: Protocol I will include 100 male cocaine abusers participating in a combined inpatient (28 days) followed by outpatient treatment program at the West Los Angeles VA Medical Center. All subjects will undergo cardiac evaluations including history & physical examination, 12 lead ECG, exercise treadmill test, 2-D echocardiogram, and 24-hour Holter monitoring. All patients will receive the identical evaluation after 4-weeks in the hospital, and 1, 3, 6, and 12 months after discharge from the hospital. The subjects can also participate in the following protocols if they are eligible according to each protocol's criteria. Protocol II will include 20 subjects with evidence of myocardial ischemia from the initial evaluation. These patients (all must have normal coronary arteries from the coronary angiograms) will undergo coronary and hemodynamic measurement before and after 48 mg of cocaine given I.V., coronary angiograms will also be repeated to rule out the possibility of cocaine-induced coronary vasopasm. Protocol II is designed to determine if cocaine adversely affect coronary circulation. Protocol III will include 20 subjects who have significant cardiac arrhythmias during the initial evaluation. These patients will undergo electrophysiologic studies including tachyarrhythmia induction before and after cocaine administration (48 mg I.V.). Patients who have inducible tachyarrhythmias during baseline will not be included. This protocol aims to determine the electrophysiologic and arrhythmogenic effects of intravenous cocaine. Protocol IV is designed to determine if I.V. cocaine (48 mg) will increase the risks of exercise as determined by exercise radionuclide ventriculography in 20 males cocaine addicts. The relationship between catecholamine and cocaine concentrations and the cardiovascular effects will be examined. Statistical analysis will include student t-test, repeated measures ANOVA, Chi square & Fisher exact tests, and univariate and multivariate analysis.